I've got an early stage of male pattern hair loss. What can be done against it?

Two things. Of all the baldness "cures", only two have clinical evidence that they work: rogaine (minoxidil) (available without a prescription) and an oral prescription drug called propecia. Use them both, and start as soon as possible, while you still have plenty of hair, since they both work better at keeping what you have than growing it back.
Several options. Non-surgical choices include Finasteride (propecia), Minoxidil (rogaine (minoxidil) and others), laser therapy (lasercap, laser combs) and transplant. Modern transplants are much more natural than the old "plugs". Follicular unit extraction (fue) is the least painful and leaves no visible scar.
Hair loss. Minoxidil (rogaine) is a solution that you apply directly to the scalp to stimulate the hair follicles. It slows hair loss for many men, and some men grow new hair. Hair loss returns when you stop using this medicine.Finasteride (propecia, proscar) is a pill that interferes with the production of a certain male hormone linked to baldness. It slows hair loss. It works a bit better than minoxidil.